Bordetellae:[unreadable] [unreadable] Bordetellae are Gram-negative bacilli causing respiratory tract infections of mammals and birds. Clinically important are B. pertussis, B. parapertussis and B. bronchiseptica. B. pertussis vaccines have been successful in preventing pertussis in infants and children. Veterinary vaccines against B. bronchiseptica are available, but their efficacy and mode of action are not established. There is no vaccine against B. parapertussis. Based on the concept that immunity to non-capsulated Gram-negative bacteria may be conferred by serum IgG anti-LPS we studied chemical, serological and immunological properties of the O-specific polysaccharides (O-SP) of B. bronchiseptica and B. parapertussis obtained by different degradation procedures. One type of the B. parapertussis and two types of B. bronchiseptica O-SP were recognized based on the structure of their non-reducing end saccharide; no cross-reaction between the two B. bronchiseptica types was observed. Competitive inhibition assays showed the immunodominance of the non-reducing end of these O-SP. Conjugates of B. bronchiseptica and B. parapertussis O-SP were prepared by two new methods: using the Kdo residue exposed by mild acid hydrolysis of the LPS or the core glucosamine residue exposed by deamination of the LPS, for binding to an aminooxylated protein. Both coupling methods were carried out at a neutral pH, room temperature, and in a short time. All conjugates, injected as saline solutions at a fraction of an estimated human dose, induced antibodies in mice to the homologous O-SP. These methodologies can be applied to prepare LPS-based vaccines against other Gram-negative bacteria.[unreadable] [unreadable] H. ducreyi:[unreadable] [unreadable] Lipooligosaccharides (LOS) of two strains of Haemophilus ducreyi, the causative agent of chancroid, were studied. The carbohydrate part of the LOS consists of either nine or six sugars terminating with partially sialylated lactosamine or lactose, respectively. Repeated subcutaneous immunization of mice with 2.5 - 5 mcg of purified LOS from either strain induced IgG responses, mostly to the inner core region. Only low levels of antibodies to the commercially obtained neolactotetraose or sialyl-neolactotetraose, containing the terminal lactosamine structure of the LOS, were detected. Antibodies induced by LOS injection did not bind to human glycolipids with terminal (sialyl)lactosamine structures, but they bound to Lipid A or Lipid A-Kdo-Kdo saccharides as assayed by immune thin-layer chromatography. These sera bound weakly to their homologous bacteria and were weakly bactericidal. Mice immunized with neolactotetraose or sialyl-neolactotetraose conjugated to human serum albumin produced low levels anti-LOS antibodies. To preserve the entire saccharide part of LOS in the conjugate we linked the 3-deoxy-D-manno-octulosonic acid (Kdo) present on the terminal reducing end of the OS to an amiooxy group of a bifunctional linker bound to carrier protein. These conjugates induced low levels of anti-LOS, mostly to the inner core, bound weakly to the homologous bacteria and had low bactericidal activity.